1. Field of the Invention
The present invention generally relates to a clutch cover assembly. More specifically, the present invention relates to a clutch cover assembly provided with a wear compensating mechanism for maintaining a pressing load in an initial state independently of wear of a friction member.
2. Background Information
A conventional clutch cover assembly of a clutch device is attached to a flywheel of an engine, and utilizes a spring force from a diaphragm spring to push a friction member of a clutch disk assembly against the flywheel to transmit a driving power from the engine toward a transmission. In this clutch device, when the friction member is worn by a predetermined amount or more, the friction member can no longer be used, or the position or attitude of the diaphragm spring of the clutch cover changes to cause a disadvantageous change in the pushing load. Accordingly, the clutch disk assembly must be replaced with a new one. Thus, there has been a demand to extend the period before this replacement and therefore to extend the life span of the clutch.
To provide a clutch with a long life span, it is important in the clutch disk assembly to increase an effective thickness of the friction member. Accordingly, approaches such as fixing friction members to a cushioning plate without using a rivet or the like have been tried.
In a clutch cover assembly, it is necessary to restore the attitude of a diaphragm spring to an initial state when the friction facing is worn. For this purpose, the clutch cover assembly is configured to determine an amount the friction facing wears, and to move a member supporting the diaphragm spring (i.e., a fulcrum ring on the pressure plate side, or a support mechanism on the clutch cover side) in accordance with the wear amount. Thereby, the friction facing of the clutch disk assembly can be used to a maximum extent.
Japanese Laid-Open Patent Publication No. H10-227317 discloses a clutch cover assembly that has a wear compensating mechanism, a biasing mechanism, and a restricting mechanism. The wear compensating mechanism primarily has a fulcrum ring arranged between a clutch cover and a diaphragm spring. The biasing mechanism biases the fulcrum ring away from a pressure plate. The restricting mechanism prevents separation of the fulcrum ring from the pressure plate and allows the fulcrum ring to move axially a distance with respect to the pressure plate. The distance corresponds to an amount of wear that has occurred on the friction facing.
A conventional friction amount detecting mechanism has an axial movement restricting portion for restoring the desired amount of axial movement, e.g., of the pressure plate with respect to the clutch cover in accordance with the wear amount. When wear occurs in the clutch engaged state, the axial movement restricting portion will operate in the next release operation to reduce the distance of movement of the pressure plate by an amount corresponding to the wear. Consequently, when the pressure plate is in the released position, the fulcrum ring is spaced from the pressure plate by a distance increased by the wear amount. After the wear is compensated, therefore, the fulcrum ring axially returns to the initial position so that the attitude or inclination of the diaphragm spring does not change.
Japanese Laid-Open Patent Publication Nos. H9-217757 and H9-14288 disclose wear compensating mechanisms that have a stopper mechanism. The stopper mechanism is provided to prevent over-adjustment (i.e., movement of the fulcrum ring away from the pressure plate by an amount larger than the wear amount) by keeping the fulcrum ring in contact with the clutch cover.
In the stopper mechanisms described above, however, when vibrations are applied to the clutch cover assembly during the clutch release operation, the pressure plate may receive a load acting to move it away from the fulcrum ring. Thereby, the pressure plate moves away from the fulcrum ring. If the fulcrum ring is spaced from the pressure plate by an amount larger than the wear amount, wear compensation cannot be accurately performed. In other words, over-adjustment can occur.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved clutch cover assembly having a wear compensation mechanism. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.
An object of the present invention is to provide a clutch cover assembly having a wear compensating mechanism, which can perform accurate wear compensation.
A clutch cover assembly in accordance with a first aspect of the present invention is configured to bias a friction facing of a clutch disk assembly toward a flywheel for engaging a clutch. The clutch cover assembly includes a clutch cover, a pressure plate, a pushing member, a biasing mechanism, a restricting mechanism, a first elastic member, and a second elastic member. The clutch cover is fixed to the flywheel. The pressure plate neighbors the friction facing, and has a first side surface opposed to the friction facing and a second side surface on the opposite side. The fulcrum ring is arranged on the side of the second side surface of the pressure plate. The pushing member is supported by the clutch cover for applying a pushing force to the fulcrum ring toward the pressure plate. The biasing mechanism applies a load to the fulcrum ring to bias the fulcrum ring away from the pressure plate. The restricting mechanism restricts movement of the pressure plate away from the friction facing in a clutch release operation, and is configured to detect an amount of wear of the friction facing. The restricting mechanism is configured to shift a stopping position of the pressure plate that has moved away from the friction facing in accordance with the wear amount toward the friction facing. The first elastic member biases the pressure plate away from the friction facing. The second elastic member biases the pressure plate and the fulcrum ring axially toward each other.
According to this clutch cover assembly, when wear occurs on the friction facing, the pressure plate and the fulcrum ring move relatively to the clutch cover toward the flywheel. When the pushing load applied by the pushing member is released from the pressure plate, the load applied by the first elastic member moves the pressure plate away from the friction facing. In this operation, the restricting mechanism stops the pressure plate at a position shifted from a position where the pressure plate was stopped before the wearing toward the friction facing by a distance or amount corresponding to the wear amount. Therefore, the fulcrum ring can axially move a distance corresponding to the wear amount after the pressure plate has stopped. Consequently, wear of the friction facing is compensated, and the attitude of the pushing member in the pushing position is restored to the attitude before the wearing.
In this clutch cover assembly, the second member biases the pressure plate and the fulcrum ring toward each other. The biasing suppresses axial movement of the pressure plate away from the fulcrum ring even when the pressure plate undergoes an acceleration due to vibrations applied to the clutch cover assembly during the clutch release operation. Thus, the over-adjustment phenomenon is suppressed in the clutch cover assembly of the present invention.
A clutch cover assembly in accordance with a second aspect of the present invention is the clutch cover assembly of the first aspect that further has such a feature that the pushing member is configured to apply a load in a direction opposite to the biasing direction of a portion of the second elastic member that biases the fulcrum ring when releasing the pushing force. This clutch cover assembly can reliably space the fulcrum ring from the pressure plate in the release operation after occurrence of wear even if the biasing force of the second elastic member is set larger than the load of the biasing mechanism for suppressing the over-adjustment.
A clutch cover assembly in accordance with a third aspect of the present invention is the clutch cover assembly of the second aspect that further has such a feature that the second elastic member is a plate spring. The second elastic member biases the pressure plate toward the fulcrum ring via a pushing portion of the pushing member. According to this clutch cover assembly, the pushing member moves the second elastic member away from the fulcrum ring in the clutch release operation. Therefore, the fulcrum ring can be spaced from the pressure plate in accordance with the wear amount in the release operation after the wear has occurred.
A clutch cover assembly in accordance with a fourth aspect of the present invention is the clutch cover assembly of the second aspect that further has such a feature that the second elastic member is in direct contact with the fulcrum ring, and the fulcrum ring is engaged with the pushing portion of the pushing member. According to this clutch cover assembly, the pushing member moves the fulcrum ring away from the pressure plate in the clutch release operation. Therefore, the fulcrum ring can be spaced from the pressure plate in accordance with the wear amount in the release operation after the wear has occurred.
A clutch cover assembly in accordance with a fifth aspect of the present invention is the clutch cover assembly of any one of the preceding aspects that has a feature such that the pushing member is a diaphragm spring having an annular elastic portion and a plurality of lever portions extending radially inward from the elastic portion. According to this clutch cover assembly, the annular elastic portion of the diaphragm spring pushes the pressure plate to engage the clutch, and the plurality of lever portions of the diaphragm spring are operated to release the pushing force of the elastic portion from the pressure plate.
A clutch cover assembly in accordance with a sixth aspect of the present invention is the clutch cover assembly of any one of the preceding aspects that further has a feature such that the pushing member stops the movement of the fulcrum ring away from the pressure plate during the wear compensating operation in the clutch release operation.
According to this clutch cover assembly, it is the pushing member instead of the clutch cover that prevents the movement of the fulcrum ring in the wear compensating operation. Therefore, not only the wear of the friction facing but also the wear of the fulcrum and support portions of various members are compensated so that the pushing member can always keep a constant attitude and position.
These and other objects, features, aspects and advantages of the present invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.